Method and apparatus for gravel packing

ABSTRACT

Method and apparatus for gravel packing a well, in which a packer is set in well casing above a production zone to isolate the zone from the casing fluids thereabove, a perforated liner assembly being disposed along the production zone, a pair of tubing strings extending from the packer to the top of the casing to provide separate flow passages for enabling fluids to be circulated to and along the production zone for the purpose of conditioning the zone, after which gravel can be pumped through one of the tubing strings into the zone and along the exterior of the liner.

Oct. 21, 1975 United States Patent 11 1 Barbee, Jr. et al.

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[75] Inventors: John P. Barbee, Jr., Luling; Charles A. Richard, Gretna, both of La.

[73] Assignee: Attorney, Agent, or Firm-William C. Norvell, Jr.

Baker Oil Tools, Inc., Los Angeles,

Calif.

[57] ABSTRACT Method and apparatus for gravel packing a well, in

22 Filed: June19, 1974 21 Appl.No.: 480,737

which a packer is set in well casing above a production zone to isolate the zone from the casing fluids thereabove, a perforated liner assembly being dis- 44 4 2m 2 ma 1 w 2 W1 6 0 MB 7 n 2 w 6 mm 1" 6 .c Hr N .e NS .L C d td UhF z Il 2 00 555 [[11 [56] References Cited UNITED STATES PATENTS ing strings into the zone and along the exterior of the liner.

2,896,714 7/1959 Killingsworth...................... 2,998,065 l-lildebrandt 3,229,767 1/1966 Carter............ 166/134 3,262,499 7/1966 Fleming.............................. 166/278 14 4 D'awmg F'gures US. Patent Oct. 21, 1975 Sheet 1 of2 3,913,676

METHOD AND APPARATUS FOR GRAVEL PACKING BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION The present invention relates to an apparatus and method for packing gravel within the bore of a subterranean well.

2. DESCRIPTION OF THE PRIOR ART Of considerable magnitude in the production of hydrocarbons such as oil and gas from a producing well is the problem of sand flow into the well bore from unconsolidated formations. Production of sand with the flow of hydrocarbons will cause the well bore to gradually fill up with minute sand particles until production perforations in the casing and, oftentimes, the end of production tubing inserted therein are covered, resulting in a significant reduction in fluid production. In many instances, sand production will cause the well to die.

In addition to reduction of fluid production, flow of sand also may cause severe damage to equipment such as pumps, chokes and the like. In flowing wells, fluid velocity may be sufficient to scavenge sand within the well bore and produce it with the fluid hydrocarbon, resulting in holes being cut in the tubing and flow lines.

One well known means of controlling flow of sand 'into the well bore is the placement of gravel on the exterior of a slotted liner to filter sand produced with the oil or gas and thus prevent its entry into production tubing. The slotted liner or screen must be designed to prevent entry of the gravel itself into the production tubing.

The reverse circulation method of packing gravel provides for pumping the gravel down the well in the annulus between the production string and the well casing. The gravel is deposited on the outer periphery of the screen assembly while the fluid returns to the top of the well through the production tubing. A pressure buildup is noted at the surface and fluid pumping stopped when the gravel covers the screen. After gravel settlement, the tubing is disconnected from the screen assembly and pulled out of the hole.

Although other fluids have been used, treated and filtered production or nearby well or surface water is preferably used in most gravel packing processes during the cleaning and washing procedure. The water is treated to remove contaminants such as cement particles, scale, and other foreign material generally resulting from the circulation of the water in the well bore. Because the volume in the annulus between the production tubing and the well casing may be as much as eight to ten times greater than the volume of the production tubing, considerably more water must be used and thus treated and filtered if clean fluid is to be used in a reverse circulation process or method than is used in conventional wash down methods.

In order to provide a gravel pack apparatus which is more efficient than prior art apparatuses and, primarily, to drastically reduce the amount of fluid which must be used during a gravel packing process, crossover equipment has been developed for use with screen assemblies and high performance packers. Such equipment now has made it feasible to gravel pack using only a fraction of the volume of fluid heretofore utilized because the fluid is maintained within the tubing and is circulated only within the treatment zone which is isolated by the packing element of the packer.

Although such an apparatus has provided many advantages over use of conventional prior art techniques, its use may be confining because it cannot be successfully utilized in high pressure wells which require the use of high density fluids, such as highly weighted muds, instead of water. If such an apparatus were utilized in conjunction with a mud system, the screen as well as the gravel pack would become plugged and would severely limit hydrocarbon production therethrough.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide an apparatus and method for gravel packing wherein the zone being gravel packed is completely isolated from well control fluid (mud) during the gravel pack operation and may remain isolated from it if desired, after completion of the gravel pack operation.

It is also an object of the present invention to provide an apparatus and method for packing gravel which reduces the required movement of tubing during the process.

It is a further object of the present invention to provide an apparatus and method for gravel packing wherein high pressures may be utilized during acidizing and squeezing of gravel into the formation.

Other objects of the present invention will be readily apparent from a reading of the FIGS, the specification below, and the claims.

The present apparatus for packing gravel within a well isolates the zone to be gravel packed from well fluid normally used to contain the well pressure. The apparatus utilizes plural or dual strings of tubing associated with a packer, which is set within the well casing with a liner assembly being attached to the packer and positioned adjacent to perforations within the well casing. The liner assembly comprises a production screen, preferably long enough to cover or straddle substantially all casing perforations to be gravel packed. The tubing strings are in sealed relation to the packer, with one of the tubing strings extending to the lower portion of the liner assembly and with another tubing string extending from the top of the well to the packer. The apparatus permits selective circulation down one string, around or through the linerv assembly and up through the other string for circulation of treating fluid or placement of gravel. The invention also incorporates a method utilizing the apparatus as above described for selectively directing the flushing and gravel packing fluids through the tubing strings and into and from the annulus around the liner assembly, as well as the interior of the liner assembly.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1a and 1b are schematic drawings of an apparatus showing a packer with a liner assembly therebelow which has been set in a well opposite casing perforations and with parallel tubing strings associated therewithin, the apparatus being positioned for circulating flushing fluids through the perforated casing region. FIG. 1b is a lower'continuation of the apparatus shown in FIG. la.

FIG. 2 is similar to FIGS. la and lb, but shows the circulating assembly in open position and the flow of fluid during gravel packing indicated by arrows.

FIG. 3 shows the upper seal means disengaged and flow of fluid for washing the interior of the liner assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention encompasses utilization of a packing mechanism 1 to the lowered end of which has been affixed a liner assembly 2. The particular packing mechanism 1 utilized is not critical to the invention and may vary considerably in design, construction and operation. It is adapted to be lowered in the well casing 9 and anchored in a packed-off condition therewithin against longitudinal movement in both upward and downward directions in a known manner. The packing mechanism 1 may generally be similar to that as detailed in U.S. Pat. No. 3,229,767. Because the packing mechanism 1 can be selected from a number of commercially available tools, and its design not being a critical part of the present invention, it is believed that the above description is more than sufficient to teach one skilled in the art its use in conjunction with the invention at hand. Therefore, further detailed elaboration of the packing mechanism 1 is not believed to be necessary.

The liner assembly 2 includes upper and lower seal receptacles 3a and 3b, each having a smooth cylindrical surface 11 extending inwardly within the bore 12 of the liner assembly 2 for sealingly engaging the upper and lower seal means a and 10b, respectively, which are affixed to a long tubular string 13, the seal means 10a and 10b each having an outer diameter only slightly larger than the internal diameter of the seal receptacles 3a and 3b, so that when each of the upper and lower seal means 10a and 10b are engagingly positioned within their respective seal receptacles 3a and 3b, fluid is prevented from traveling therebetween. This can generally be accomplished by utilizing a seal means 10a and 10b having a slightly flexible rubber-like outer lip surface 14 which will compress slightly when urged into.

sealing position within the respective seal receptacles 3a and 3b.

Spaced vertically on the liner assembly 2 on the lower portion thereof below and adjacent to a tubing section 5 is a production screen 6 having a desired permeability to allow the transfer of flushing fluids but to block out the flow of sand and gravel. A tell tale screen section 4 is spaced above and adjacent to the tubing section 5 for a purpose which will hereinafter described. Below the production screen 6 is a second section of tubing and a lower seal receptacle 312 for the sealing engagement of the lower end of the long tubular string 13. Below the lower seal receptacle 3b is a discharge valve 7 which prevents entry of well fluids within the liner assembly to the casing annulus 9a.

The liner assembly 2 and the packing mechanism 1 form a housing for the dual string assembly 16 which comprises a parallel flow tube 17 threadedly connected to the tubular long string 13 run into the well and serves to sealably engage a second string of tubing 19 and to also sealably engage with the bore la of the packing mechanism 1 by means of circumferentially extending seals 22, which are of a similar construction as seals 10a and 10b. Thus, when the dual string assembly 16 is positioned within the packing mechanism 1, there can be no communication of fluid from above to below the packing mechanism 1 except through the tubular strings 13 and 19. The parallel flow tube 17 provides separate passages 20 and 21 through the packing mechanism 1 for respective flowing engagement between the tubing strings l3 and 19 and conducts fluid to or from. the liner assembly 2, as will be described in more detail below.

The parallel flow tube 17 has a series of circumferentially extending and slightly outwardly protruding seal means 22 to permit adequate longitudinal movement of the tubular strings 13 and 19 without inadvertent disen gagement of the seals 22 from the bore 1a of the packing mechanism 1 during limited raising or lowering of the tubular strings l3 and 19 in the practice of the method,as will be described.

Immediately above the seal means 22 on the parallel flow tube 17 is an enlargement or shoulder 23 which can engage the upper end of the packer bore 1a 'of the packing mechanism 1 and which serves as a stop to limit downward travel of the parallel flow tube 17 through the packing mechanisml. The first passage way 20 in the parallel flow tube 17 houses a nipple 26 on the upper end for connection of the upper portion 13a of the long tubular string 13. The passageway 20 provides a flow path between the upper portion 13a of the tubular long string 13 and the lower portion 13b thereof in the liner assembly 2. Forming the upper por- 7 tion of passageway 21 is a circumferentially extending smooth seal surface 25 which will sealably engage with a seal assembly 27 run on the second or short string of tubing 19. The lower end of the passageway 21 opens into the bore 12 between the exterior of the lower portion 13b of the long tubular string 13 and the interior.

means 10b is a circulating assembly 32 having a tubular housing 33 with a series of circumferentially spaced ports 34 which are initially closed by means of a vertical sliding internal sleeve 35 also initially secured to the tubular housing 33 by means ofa shear screw 36 within a bore 36a. The sliding sleeve 35 has a ball seat 37 in the uppermost portion thereof as well as a series of elastomeric side seals 38, which initially prevent escape of fluid between the sleeve 35 and the tubularhousing 33 when the ports 34 are in initially close position as the result of the engagement of the sleeve 35 by the shear screw 36. At the lowerend of the tubular housing 1 33 is a shoulder 39 for the limitation of lower travel of the sliding sleeve 35. As detailed hereinafter, a ball 40 inserted at the top of the well through the long tubular string 13 will gravitate or can'be pumped down the string 13 to sealingly engage the seat 37. i

The dischargevalve 7 positioned on the lower portion of the liner assembly 2 is a check valve permitting.

downward flow and preventing upward flow of fluid. Although several common and known discharge valves 7 could be utilized for this purpose, a spring loaded mushroom shaped poppet valve 7 is depicted in open position in FIG. 1b.

The liner assembly 2'also has a series of circumferen tially spaced ports 8 above the seal receptacle 3a for the travel of fluid between the bore 12 of the liner as-' sembly 2 to the casing annulus 9a.

OPERATION OF THE METHOD In order to establish a base to support the gravel pack, a bridge plug B-P may be set below the lowermost end of the perforations P.

The packing mechanism 1 with the liner assembly 2 attached thereto is set at a predetermined depth within the casing annulus 9a in the well prior to initiation of the gravel packing operation. The setting mechanism is withdrawn and returned to the well surface. After the packing mechanism 1 has been set, the parallel flow tube 17 is lowered into the well on the long tubular string 13a until the tube 17 enters the bore 1a of the packing mechanism 1 and so that the upper and lower seal means a and 10b, are respectively sealingly engaged within their receptacles 3a and 3b of the liner assembly 2 and, concurrently, the seal means 22 on parallel flow tube 17 are sealingly engaged in the bore 1a of the packing mechanism 1. The short tubular string 19 is then run into the well and communicatingly affixed to the passageway 21 within the parallel flow tube 17. The entire apparatus A now is in condition for initiation of the gravel packing procedure.

At this point, a flushing fluid is pumped from the top of the well through the long tubular string 13, exiting the long tubular string 13 through the opened discharge valve 7 (which is urged openly by the pressure within the long tubular string 13) and travels to the outside of the liner assembly 2 and into the annulus 9a of the well casing 9. As the flushing fluid rises in the annulus 9a, the contaminated well fluid is displaced from the annulus 9a into the liner assembly 2 through the ports 8 in the upper portion of the liner assembly 2 and flows through the tubular short string 19 to the top of the well for disposal.

Upon completion of the step as described above, the ball 40 is pumped down the long tubular string 13 until it comes to rest on the seat 37. Application of pressure to the long tubular string 13 then pumps the sliding sleeve 35 downward, first shearing the shear screw 36 and then exposing the ports 34. Downward movement of the sliding sleeve 35 is limited by contact of the lower end of the sleeve 35 with the shoulder 39. The placement of the ball 40 on the ball seat 37 sealingly prevents subsequent pumping or flow of fluid through the lower portion 13b of the long tubular string 13 and will permit fluid to travel in the annulus 28 between the liner assembly 2 and the long tubular string 13 because of the exposure and open position of the ports 34.

Thereafter, flushing fluid is reverse circulated down the short string 19 and through the ports 8 in the liner assembly 2 above the upper seal receptacle 3a. The fluid travels downwardly in the annulus 9a of the well casing 9 and re-enters the liner assembly 2 through the porous production screen 6 and the tell tale screen 4, thereby cleaning each of the screens 6 and 4 and displacing well fluid upwardly by means of opened ports 34 within the circulating assembly 32 on the lower portion 13b of the tubular long string 13. The fluid travels to the surface of the well upwardly through the tubular long string 13 for subsequent disposal.

Thereafter, gravel is pumped down the short tubing string 19, exiting the liner assembly 2 through the ports 8 and traveling into the annulus 9a of the casing 9. The pumping of the gravel is continued and pressure is exerted within the short tubing string 19 in order to squeeze the gravel behind the perforations P. A valve (not shown) on the long tubular string 13 is opened at the surface of the well and the gravel packing is continued until the bore 9a is filled with gravel particles and until an increase in back pressure indicates that the tell 'tale screen 4 has been covered with gravel.

Upon notation at the well surface of an increase in :back pressure, the tubular strings 13 and 19 are raised so that the upper seal means 10a are disengaged from the upper seal receptacle 3a. Fluid then is circulated down the long tubular string 13 through the annular area or bore 12 of the liner assembly 2 and back to the surface through the tubular short string 19 to wash out any flne particles of sand or gravel that may have passed through the screens 4 and 6 to the annular area 12. The fluid exits the liner assembly 2 through the opened ports 34 below the production screen 6 and travels in the annulus 12 between the lower portion 13b of the tubular string 13 and the liner assembly 2 past the tell tale screen 4 and exits the part of the liner assembly 2 below the upper seal receptacle 3a through the canal 47 resulting from the disengagement of the upper seal means 10a from the upper seal receptacle 3a and continues upwardly to the top of the well through the tubular short string 19. The circulating of the fluid may be reversed if desired.

After the above described step is completed, both strings of tubing 13 and 19 may be lowered to their original position and the well put on production. Alternatively, the strings l3 and 19 may be pumped full of mud to kill the well so that the strings 13 and 19 can be safely removed from the well. Subsequently, the well can be completed with one string of tubing with seals on its lower end inserted into the bore la of the packing mechanism 1.

Although the invention has been described in terms of specified embodiments which are set forth in detail, it should be understood that this is by illustration only and that the invention is not necessarily limited thereto, since alternative embodiments and operating techniques will become apparent to those skilled in the art in view of the disclosure. Accordingly, modifications are contemplated which can be made without departing from the spirit of the described invention.

What is claimed and desired to be secured by Letters Patent is:

1. An apparatus for use in a subterranean well having a production zone and fluid in said well, comprising: isolation means for isolating the production zone from the fluid in the well above the zone, said means defining first and second fluid passages communicating with the zone and having means adapted to receive first and second tubular strings extending from said means to the top of the well; a liner assembly carried by and depending from said isolation means, said assembly including a first perforated member through which fluid can flow between the exterior and the interior of said member, said assembly having means for providing fluid in communication with said first fluid passage and the exterior of said perforated member; a second tubular member within said liner assemblyproviding a fluid passageway communicating with said second fluid passage and communicable with the interior of said perforated member; and means for selectively controlling fluid flow in said passageway.

2. The apparatus as defined in claim 1 wherein said means for selectively controlling fluid flow includes a portin said second tubular member opening into the interior of said perforated member; and valve means in said second tubular member movable between positions closing and opening said port.

3. The apparatus as defined in claim 1 wherein said means for selectively controlling fluid flow includes a port in said second tubular member opening into the interior of said perforated member; a sleeve valve member closing said port; and means engaging said sleeve valve member for shifting said sleeve valve member to port opening position.

4. The apparatus as defined in claim 1 wherein said means for selectively controlling fluid flow includes a port in said second tubular member opening into the interior of said perforated member; valve means in said second tubular member closing said port; downwardly opening valve means in said liner member below said perforated member through which fluid flowing through said second tubular member can flow into the well externally of said liner assembly; and means for shifting said first mentioned valve means to port opening position.

5.The apparatus as defined in claim 1 wherein said means for selectively controlling fluid flow includes a port in said second tubular member opening into the interior of said perforated member; a sleeve valve member closing said port; means engaging said sleeve valve member for shifting said sleeve valve member to port opening position; downwardly opening valve means in said liner assembly below said perforated member through which fluid flowing through said second tubular member can flow into the well externally of said liner assembly.

6.,An apparatus for use in a subterranean well having a production zone and fluid in said well, comprising: a well packing mechanism; a liner assembly connected to and extending below said packing mechanism, said assembly including a perforated member having perforations sized to prevent entry of particulate matter through the perforations into the interior of said perforated member; first and second interior seal receptacles on opposite ends of saidperforated member; means having first and second flow passages therethrough and sealed within the well packing mechanism, said first and second flow passages being adapted to be placed in communication with first and second tubular strings, respectively, extending to the top of the well; a tubular extension within said liner assembly adapted to communicate with said first tubular string and providing at least a part of said first fluid passage; first and second seal means on said tubular extension for respective selective sealing engagement with said first and second interior seal receptacles; means on the liner assembly above said first seal receptacle defining a fluid passageway providing at least a part of said secondfluid passage; and means for selectively controlling fluid flow in said first and second flow passages.

7. The apparatus as defined in claim 6, wherein said means for selectively controlling fluid flow includes a port in said tubular extension opening into the interior of said perforated member; and valve means in said tubular extension movable betweenpositions closing and member for shifting said sleeve valve member toport opening position.

9. The apparatus as defined in claim 6 wherein said means for selectively controlling fluid flow includes a port in said tubular extension opening into the interior of said perforated member; valve means in said tubular extension closing said port; downwardly opening valve means in said liner member below said perforated. member through which fluid flowing through said tubular extension can flow into the well externally of said I liner assembly; and means for shifting said firstmentioned valve means to port opening position.

10. The apparatus as defined in claim 6 wherein said means for selectively controlling fluid flow includes a port in saidtubular extension opening into the interior 11. The apparatus as defined in claim 6; saidtubular extension and said means sealed within the well packing mechanism being longitudinally shiftable to remove the upper of said seal means from the upper of said interior seal receptacles while said seal of said means within the well packing mechanism remains to enable fluid to flow from the interior of said tubular extension into the interior of said perforated liner. for upward flow of fluid into the second flow passage.

12. The apparatus as defined in claim 6 wherein said.

means for selectively controlling fluid flow includes a port in said tubular extension opening into the interior of said perforated member; valve means in said tubular extension movable between positions closing and opening said port; said tubular extension and said means sealed within the well packing mechanism being longitudinally shiftable to remove the upper of said seal means from the upper of said interior sealreceptacles while said seal'of said means within the well packing mechanism remains to enable fluid to flow from the interior of said tubular extension into the interior of said perforated liner for upward flow of fluid into the second flow passage.

13. The apparatus as defined in claim 6 wherein said means for selectively controlling fluid flow includes a port in said tubular extension opening into the interior of said perforated member; a sleeve valve member closing said port; means engaging said sleeve valve member for shifting the said sleeve valve member to port opening position; downwardly opening valve means in said liner assembly below said perforated member through which fluid flowing through said tubular extension can flow into the well externally of said liner assembly; said tubular extension and said means sealed within the well packing mechanism being longitudinally shiftable to remove the upper of said seal means from the upper of i said interior seal receptacles while said seal of said means within the well packing mechanism remains to enable fluid to flow from the interior of said tubular extension into the interior of said perforated liner for upward flow of fluid into the second flow passage.

14. A method for gravel packing a production zone in a well comprising the steps of: running a well packing mechanism with a perforated liner depending therefrom in the well and setting said mechanism in the well gravel down one of said strings and through its associated fluid passage into the zone surrounding the perforated liner, the fluid in advance of the fluid containing gravel and in the zone surrounding the perforated liner flowing through the other fluid passage and the other of said strings to the top of the well. 

1. An apparatus for use in a subterranean well having a production zone and fluid in said well, comprising: isolation means for isolating the production zone from the fluid in the well above the zone, said means defining first and second fluid passages communicating with the zone and having means adapted to receive first and second tubular strings extending from said means to the top of the well; a liner assembly carried by and depending from said isolation means, said assembly including a first perforated member through which fluid can flow between the exterior and the interior of said member, said assembly having means for providing fluid in communication with said first fluid passage and the exterior of said perforated member; a second tubular member within said liner assembly providing a fluid passageway communicating with said second fluid passage and communicable with the interior of said perforated member; and means for selectively controlling fluid flow in said passageway.
 2. The apparatus as defined in claim 1 wherein said means for selectively controlling fluid flow includes a port in said second tubular member opening into the interior of said perforated member; and valve means in said second tubular member movable between positions closing and opening said port.
 3. The apparatus as defined in claim 1 wherein said means for selectively controlling fluid flow includes a port in said second tubular member opening into the interior of said perforated member; a sleeve valve member closing said port; and means engaging said sleeve valve member for shifting said sleeve valve member to port opening position.
 4. The apparatus as defined in claim 1 wherein said means for selectively controlling fluid flow includes a port in said second tubular member opening into the interior of said perforated member; valve means in said second tubular member closing said port; downwardly opening valve means in said liner member below said perforated member through which fluid flowing through said second tubular member can flow into the well externally of said liner assembly; and means for shifting said first mentioned valve means to port opening position.
 5. The apparatus as defined in claim 1 wherein said means for selectively controlling fluid flow includes a port in said second tubular member opening into the interior of said perforated member; a sleeve valve member closing said port; means engaging said sleeve valve member for shifting said sleeve valve member to port opening position; downwardly opening valve means in said liner assembly below said perforated member through which fluid flowing through said second tubular member can flow into the well externally of said liner assembly.
 6. An apparatus for use in a subterranean well having a production zone and fluid in said well, comprising: a well packing mechanism; a liner assembly connected to and extending below said packing mechanism, said assembly including a perforated member having perforations sized to prevent entry of particulate matter through the perforations into the interior of said perforated member; first and second interior seal receptacles on opposite ends of said perforated member; means having first and second flow pAssages therethrough and sealed within the well packing mechanism, said first and second flow passages being adapted to be placed in communication with first and second tubular strings, respectively, extending to the top of the well; a tubular extension within said liner assembly adapted to communicate with said first tubular string and providing at least a part of said first fluid passage; first and second seal means on said tubular extension for respective selective sealing engagement with said first and second interior seal receptacles; means on the liner assembly above said first seal receptacle defining a fluid passageway providing at least a part of said second fluid passage; and means for selectively controlling fluid flow in said first and second flow passages.
 7. The apparatus as defined in claim 6, wherein said means for selectively controlling fluid flow includes a port in said tubular extension opening into the interior of said perforated member; and valve means in said tubular extension movable between positions closing and opening said port.
 8. The apparatus as defined in claim 6 wherein said means for selectively controlling fluid flow includes a port in said tubular extension opening into the interior of said perforated member; a sleeve valve member closing said port; and means engaging said sleeve valve member for shifting said sleeve valve member to port opening position.
 9. The apparatus as defined in claim 6 wherein said means for selectively controlling fluid flow includes a port in said tubular extension opening into the interior of said perforated member; valve means in said tubular extension closing said port; downardly opening valve means in said liner member below said perforated member through which fluid flowing through said tubular extension can flow into the well externally of said liner assembly; and means for shifting said first-mentioned valve means to port opening position.
 10. The apparatus as defined in claim 6 wherein said means for selectively controlling fluid flow includes a port in said tubular extension opening into the interior of said perforated member; a sleeve valve member closing said port; means engaging said sleeve valve member for shifting said sleeve valve member to port opening position; downwardly opening valve means in said liner assembly below said perforated member through which fluid flowing through said tubular extension can flow into the well externally of said liner assembly.
 11. The apparatus as defined in claim 6; said tubular extension and said means sealed within the well packing mechanism being longitudinally shiftable to remove the upper of said seal means from the upper of said interior seal receptacles while said seal of said means within the well packing mechanism remains to enable fluid to flow from the interior of said tubular extension into the interior of said perforated liner for upward flow of fluid into the second flow passage.
 12. The apparatus as defined in claim 6 wherein said means for selectively controlling fluid flow includes a port in said tubular extension opening into the interior of said perforated member; valve means in said tubular extension movable between positions closing and opening said port; said tubular extension and said means sealed within the well packing mechanism being longitudinally shiftable to remove the upper of said seal means from the upper of said interior seal receptacles while said seal of said means within the well packing mechanism remains to enable fluid to flow from the interior of said tubular extension into the interior of said perforated liner for upward flow of fluid into the second flow passage.
 13. The apparatus as defined in claim 6 wherein said means for selectively controlling fluid flow includes a port in said tubular extension opening into the interior of said perforated member; a sleeve valve member closing said port; means engaging said sleeve valve member for shifting the said sleeve valve member to port opening position; downwardly opEning valve means in said liner assembly below said perforated member through which fluid flowing through said tubular extension can flow into the well externally of said liner assembly; said tubular extension and said means sealed within the well packing mechanism being longitudinally shiftable to remove the upper of said seal means from the upper of said interior seal receptacles while said seal of said means within the well packing mechanism remains to enable fluid to flow from the interior of said tubular extension into the interior of said perforated liner for upward flow of fluid into the second flow passage.
 14. A method for gravel packing a production zone in a well comprising the steps of: running a well packing mechanism with a perforated liner depending therefrom in the well and setting said mechanism in the well above the production zone; providing first and second fluid passages extending within the well packing mechanism; providing first and second tubular strings communicating with said first and second fluid passages, respectively, and extending to the top of the well, said first fluid passage extending into the perforated liner, said second fluid passage communicating with the exterior of the perforated liner; pumping fluid containing gravel down one of said strings and through its associated fluid passage into the zone surrounding the perforated liner, the fluid in advance of the fluid containing gravel and in the zone surrounding the perforated liner flowing through the other fluid passage and the other of said strings to the top of the well. 